How to use data validation

Data Validation is a function provided by Excel to limit users from entering
value other than those pre-defined. For example, you might want the user
to enter only values between 0 and 200. You can set the limit using this
function. In the following example, I have used it to limit users from
entering values or text other than those in the list which I have pre-defined.

a. Select the cell in the worksheet where you want to limit user to certain values.